This thesis investigates the fouling of a microfiltration membrane by biological solutions. Membrane fouling is recognized as a major drawback for the application of microfiltration in the purification of biotechnology products. Membrane fouling was analyzed and compared for filtrations performed with a hollow fiber microfiltration module operated at constant permeate flux using bovine serum albumin (BSA) solutions or Chinese hamster ovary (CHO) cell culture broths as feed solutions. A mechanistic model was developed to represent the fouling of a cross-flow microfiltration membrane operated at constant permeate flux. Fouling was observed as an increase in the transmembrane pressure (TMP) and assumed to occur first by pore blockage followed by cake formation over the blocked pores. The effect of the cross-flow action was described by the removal of deposits from the membrane surface thereby reducing the pore blockage and the mass of the cake. The model was fitted to the TMP profiles obtained during the filtration of BSA solutions and Chinese hamster ovary (CHO) cell culture broths with a 0.45 µm polysulfone hollow fiber membrane. According to the fitted model, pores blocked faster and more cake was formed with increasing BSA concentration. In the case of CHO cell culture broth, increasing the wall shear rate (proportional to cross-flow velocity) seemed to lead to the formation of a less pronounced cake but more pore blockage. The cross-flow mechanistic model was applied to the microfiltration of CHO cell culture supernatants harvested at different days of the fermentation process. The filtrations were performed at two different shear rates and with two different membrane pore sizes. The cell culture supernatant caused membrane fouling observed as an increase in both the TMP and the membrane hydraulic resistance estimated from water flux measurements at the end of the filtrations. The highest TMP increase was observed for the filtrations with the smaller membrane pore size (0.2 µm) and the higher shear rate (8000 s-1). The hydraulic resistance estimates of the fouled membrane also revealed a higher irreversible fouling for the smaller (0.2 µm) membrane pore size while the model analysis indicates that more fouling occurred at the entrance of the membrane pores. The shear rate was found to strongly influence the contribution of the reversible fouling to the total hydraulic resistance of the membrane. The cross-flow mechanistic model indicates a higher pore blockage for the most severe membrane fouling observed experimentally for the smaller membrane pore size and the higher shear rate. At the same time, a smaller cake deposit was predicted for the higher shear rate. The different cell culture harvest time investigated in this study did not reveal any differences in membrane fouling. BSA solutions were used to evaluate the contribution of BSA aggregates, fresh cell culture medium and the non-ionic surfactant Pluronic F-68 to membrane fouling. A simple empirical model was developed to represent the TMP increase and to derive the initial fouling rate. The initial fouling rate, the normalized TMP and the irreversible membrane resistance at the end of the filtration were analyzed to determine the effect of BSA solution characteristics on membrane fouling. The initial fouling rate increased with increasing BSA aggregate content consistent with a two-step fouling mechanism that was proposed for membrane fouling by BSA. Increased BSA concentration and the use of fresh cell culture medium compared to potassium phosphate buffer resulted in an increase in initial fouling rate, TMP and irreversible membrane fouling. The addition of the non-ionic surfactant Pluronic-F68 to the BSA solutions decreased the long-term fouling and the irreversible fouling but did not affect the initial fouling rate.

Abstract The Balance Balanus albicostatus is the dominant species of fouling organism in Kaohsiung Port. In different harbor district environments In Kaohsiung Port, one can discriminate the population of B. albicostatus into three different groups¡Gthe estuary area of Love River, the outer harbor area, and the harbor area. The variation of estuary area¡¦s (Jhongjheng Bridge Station on Love River) population is the highest with the averaged survival rate of 53.8¡Ó21.7%. The population in the harbor area (The First Harbor Mouth station) is more stable with the averaged survival rate of 62.5¡Ó8.1%. The composition of population in the eliminated area in all stations after one year is similar to the previous one. It is suggested that barnacle population in Kaohsiung port can recover from environmental disturbance throughout larval recruitment within a year. Based on the results from the growth experiment of the settled barnacle¡¦s larvae, it was indicated that the growth and survival rate of the settled larvae was least affected by the recruitment of any kinds of settled larvae including barnacle itself. To understand the influence of environmental factors on the hatching of egg and development of larvae, we cultivated the larvae of B. albicostatus under the control of temperatures and salinities in the laboratory. The hatching rate of egg and times required for larvae to metamorphosis at each stage is the shortest under the condition of high temperature and high salinity. The larvae can metamorphose into cyprid in five days after hatching at the high temperature (35¢J), while it is prolonged to 19 days after hatching under the low temperature (15¢J) and low salinity (22 psu). The settlement rate of cyprids is better under high salinity (33 psu). To understand the effects of biofilm on settlement of cyprids, the biofilms are cultured under the conditions of the non-filtered, 80£gm, 20£gm, and 1£gm filtered seawater. When the biofilms have grown for 5 days, the settlement rate of cyprids on the biofilm cultured by the filtered seawater is higher than those on the non-filtered biofilms and alcohol-sterilized ones. At the day 12, the 1£gm filtered treatments had a greatest quantity of settled larvae while the number of settled cyprids in the other treatments decreased. The number of settled cyprids on panels with biofilms cultured for 15 days in non-filtered seawater and the one with biofilms fallen off for more than 75% of the total area did not significantly differ from the one with biofilms cultured in the seawater filtered with the 1£gm mesh. This showed that biofilms cultured under different filtered conditions affect the settlement of cyprids over time. It is concluded that the population of barnacle Balanus albicostatus, based on survival rate and growth, can be grouped into three different groups in the Kaohsiung Port. From the laboratory experiments, it is showed that the type of biofilm and the aging processes over time can affect the settlements of cyprids. It therefore suggested that the larval recruitments of the barnacle B. albicostatus can be affected by the types of biofilm on the different substrates, and consequently the larval recruitments in the different environmental conditions in Kaohsiung Port.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on March 18, 2010. Major professor: Dean E. Wendt, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Biological Sciences." "March, 2010." Includes bibliographical references (p. 53-61).

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Knox T. Millsaps, Jr. Includes bibliographical references (p. 48-56). Also available online.

Thesis (Ph. D.)--University of Hong Kong, 1983. / Also availalbe in microfilm.

The study reported here was aimed at optimising the microfiltration (MF) membrane process applied to water reclamation. Polypropylene hollow fibre membrane (0.2 ??m) with high pressure backwahing was mainly used in this study. To obtain secondary effluent for microfiltration a biological treatment (UASB/SBR) was applied to brewery effluent. It was identified that loading at a rate below 14 kg COD/kLd will ensure the stable performance of UASB. An initial energy balance of the system (Biological and MF) shows a plant treating brewery effluent (4000 mg/L COD) could yield a net energy of 2.5 kWh/kL (yield from methane less the plant operating energy) at an optimised MF flux. For the MF of low solids feed it was found that crossflow has no benefit and that intermittent dead end filtration is less productive than dead-end cycles. It was also that found cycle time between air backwashes is strongly dependent on the imposed flux and the maximum TMP allowed. Analysis based on energy and capital cost indicates that if energy saving is the objective the unit needs to be operated at low imposed flux. However, if capital and energy costs are combined, cost efficient operation would be at about 60 to 70 L/m2.h for TMPmax of 20 kPa or above 80 L/m2.h for TMPmax of 50 kPa. For cycles with a TMPmax of 20 kPa, the specific cake resistance was constant over the range of imposed fluxes. However, for a TMPmax of 50 kPa the specific resistance was higher and increased with imposed flux, signifying compressible cake formation. Further analysis of the TMP profiles showed that the membrane resistance increased over a number of cycles and that the increase was higher at higher flux. To fully optimise the operation, it would be necessary to include these factors. Laboratory scale studies with yeast showed many similarities with secondary effluent filtration. However, some inconsistencies were observed at lower f1uxes, which need to be confirmed by further studies. Life cycle assessment of the membrane filtration process indicated that operating at low flux (10 Llm2.h) with higher TMPmax is the environmentally sound operational strategy. The analysis highlights the fact that the environmental impacts mainly come from the membrane operation (more than 85%). When alternative energy sources are considered, the least impact operational strategy shifts towards higher flux (in the vicinity of 30 l/m2.h). In-situ electrochemical cleaning using an electrolysis process indicated better flux recovery than traditional chemical cleaning. However, repeated cycles of fouling and cleaning showed electrochemically cleaned membranes have a higher fouling tendency than the chemically cleaned membrane. Initial characterisation of membrane surface properties after cleaning could not provide conclusive evidence for the cause of rapid fouling of the electrochemically cleaned membrane.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Ph.D. in Marine Environmental Science. Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--University of New South Wales, 2002. / Also available online.

Thesis (Ph. D.)--University of New South Wales, 2004. / Also available online.

Univ., Diss.--Göteborg, 2005. / Enth. außerdem 5 Zeitschriftenaufsätze.